JP2009527095A - Carbon nanotube lithium metal powder battery - Google Patents

Abstract

  A high energy lithium battery system is disclosed. This system includes carbon nanotubes and / or other nanotube materials, both anode and cathode. The anode is lithiated using lithium metal powder.

Description

DESCRIPTION OF FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT This invention was made in part with United States government support from the Office of Naval Research under contract number N0014-03-M0092. The United States government may have certain rights in the invention.

  The present invention relates to an energy storage device. In particular, the present invention relates to a lithium ion battery having two active electrodes composed of carbon nanotube (CNT) material, wherein lithium metal powder is dispersed in the anode CNT material.

  Future portable power sources for consumer and military applications are likely to require greater specific energy and power from lithium battery technology. In order to meet future power requirements, lithium batteries are expected to have a sustained specific energy of over 400 Wh / kg and have a pulse power capability of over 2 kW / kg at 100 Wh / kg. In addition, these systems may need to operate effectively over a wide temperature range (-20 to 90 ° C) and be capable of rapid recharging. These requirements cannot be met by conventional batteries or by extrapolating the capabilities of conventional systems. As is well known, conventional Li ion electrode materials are subject to physical and chemical constraints that limit lithium storage capacity.

Conventional commercial lithium ion battery technology relies on lithiated metal oxides for the positive electrode (cathode) and carbon (in various forms) as the negative electrode (anode). The Li-ion cell begins its life with all the lithium in the cathode, and a percentage of this lithium is transferred to the anode by charging and inserted into the carbon anode. When the charging process is complete, the cell has an open circuit voltage of about 4.2V. This cell voltage of about 1.15 V is due to the positive potential of the metal oxide electrode. The high chemistry of these two materials ensures a high open circuit potential. However, it can be imagined that materials with similar chemistry will produce similar results. In 1980, it was proposed by Lazzari and Scrosati to use a “rocking chair concept”, ie two intercalation compounds based on metal oxides or metal sulfides (non-patent literature). 1, the entire teachings of which are incorporated herein by reference. A Li _x WO ₂ / Li _y TiS ₂ cell working at an average voltage of 1.8 V has been described. While this system has solved the problem of metallic lithium anodes, it has not been possible to provide the practical energy density required for a viable alternative to existing rechargeable systems. After this preliminary report, researchers found that certain types of carbon could reversibly intercalate lithium and withdrew from the use of two metal oxide electrodes. The most graphitized carbon gives a stoichiometry of LiC ₆ (375 mAh / g), while disordered carbon generally gives Li _x C ₆ (x> 1) (400 mAh / g). Compared to lithiated carbon, lithium metal anodes have a theoretical capacity of> 3000 mAh / g and an actual capacity of 965 mAh / g (Non-Patent Document 2, the entire teachings of which are incorporated herein by reference. Part).

Carbon nanotubes are attracting attention as potential electrode materials. Carbon nanotubes often exist as closed concentric multi-layer shells or multi-walled nanotubes (MWNTs). Nanotubes can also be formed as single-walled nanotubes (SWNT). SWNTs form bundles, which have a tightly packed 2-D triangular lattice structure. Both MWNTs and SWNTs have been manufactured, and the specific capacity of these materials has been evaluated by gas phase reactions. For example, see Non-Patent Document 3, Non-Patent Document 4, Non-Patent Document 5, and Non-Patent Document 6, the entire teachings of which are incorporated herein by reference. The maximum alkali metal saturation value for these nanotube materials was reported as MC ₈ (M = K, Rb, Cs). These values do not represent a significant advantage over existing commercially used materials such as graphite. Recent experimental results have demonstrated that single-walled carbon nanotubes can be loaded on Li ₁ C ₃ and above. The capacity of the crude material has been experimentally determined to exceed 600 mAh / g. These capacities have begun to approach the capacities of pure lithium, but avoid lithium safety concerns. In addition, as mesophase carbon microbeads (MCMB), since lithium is reversibly intercalated, carbon nanotubes have gained dramatic improvements over MCMB as anode materials. It is clear that carbon nanotubes offer new possibilities for high energy batteries and may offer new opportunities for completely new battery designs that could not be obtained with conventional electrode materials.

Lithiated carbon nanotubes (CNTs) have been reported in the scientific and patent literature as a means of providing high energy non-metallic anodes for lithium batteries. Specifically, Patent Document 1, Patent Document 2 and Patent Document 3, the entire teachings of which are incorporated by reference and made a part of this specification, describe in detail how to produce laser-generated carbon nanotubes and their lithiation. It is described. However, the prior art does not include the concept of using a lithium metal powder / CNT anode and a CNT cathode to form a high energy battery.
US Pat. No. 6,280,697 US Pat. No. 6,422,450 US Pat. No. 6,514,395 M. Lazzari and B. Scrosati, J. Electrochem. Soc, Brief Communication, March 1980 Linden, D. and Reddy, TB, Handbook of Batteries, 3rd ed.p34.8, McGraw-Hill, NY, 2001 O. Zhou et al., Defects in Carbon Nanotubes, Science: 263, pgs. 1744-47, 1994 RS Lee et al., Conductivity Enhancement in Single- Walled Nanotube Bundles Doped with K and Br, Nature: 388, pgs. 257-59, 1997 AM Rao et al., Raman Scattering Study of Charge Transfer in Doped Carbon Nanotube Bundles, Nature: 388, 257-59, 1997 C. Bower et al., Synthesis and Structure of Pristine and Cesium Intercalated Single- Walled Carbon Nanotubes, Applied Physics: A67, pgs. 47-52, spring 1998

  The present invention relates to a high energy lithium battery system. According to some embodiments of the present invention, an anode in electrical communication with the cathode, a separator separating the anode from the cathode, and means for electrical communication between the anode and the cathode, the cathode and A battery is provided wherein the anode comprises CNTs and the anode, and optionally the cathode, is lithiated with lithium metal powder.

  In some embodiments, the CNT electrode is a single layer, multilayer, nanohorn, nanobell, peapod, buckyball and the like, or other colloquial name for nanostructured carbon materials. Or any combination thereof.

  These and other features of the present invention will be readily apparent to those of ordinary skill in the art in view of the following detailed description and accompanying drawings that describe both preferred and alternative embodiments of the invention.

  The present invention can be more easily confirmed by reading the following description of the present invention in conjunction with the accompanying drawings.

  In accordance with the present invention, an anode in electrical communication with a cathode, a separator that separates the anode from the cathode, and means for electrical communication between the anode and the cathode, the cathode and A battery is provided wherein the anode comprises CNTs, and the anode, and optionally the cathode, is lithiated with lithium metal powder.

  For the purposes of the present invention, the term “battery” refers to a single electrochemical cell, or unicell, and / or one or more electrochemically connected in series and / or in parallel known to those skilled in the art. It is understood that a cell can be meant and included. Further, the term “battery” includes, but is not limited to, rechargeable batteries and / or secondary batteries and / or electrochemical cells.

  A battery according to an embodiment of the present invention may include a positive electrode (cathode) and a negative electrode (anode), a separator separating the cathode and the anode, and an electrolyte in communication with the cathode and the anode. Here, both electrodes include a carbon nanotube (CNT) material capable of absorbing and desorbing lithium in an electrochemical system, and lithium metal powder is dispersed in the anode, and possibly the cathode CNT.

  FIG. 1 shows an embodiment of the present invention. The illustrated battery system 1 comprises an anode 3, a cathode 5, a separator 7, and means 8 for promoting electrical communication between the anode 3 and the cathode 5. In one aspect of this embodiment, the anode 3 and the cathode 5 are composed of CNT materials having various structures. The CNT material can be multi-layer, single-layer, nanohorn, nanobell, peapod, buckyball or any other known nanostructured carbon material. The separator 7 includes an insulating material (one or a plurality of types) having a liquid or polymer cation conductive electrolyte. Means 8 for electrical communication between anode 3 and cathode 5 include any known means for facilitating electrical communication between anode and cathode. Such means include, but are not limited to, suitable low resistance wires.

  As described in detail below, the cathode and anode include CNTs, where the anode, and optionally the cathode, includes lithium metal powder dispersed therein. Throughout this specification, it should be understood that the general term CNT refers to the entire set of carbon nanotube materials well known to those skilled in the art. In some embodiments, the CNT electrode comprises a single layer, multilayer, nanohorn, nanobell, peapod, buckyball and the like, or other colloquial names for nanostructured carbon materials, or any combination thereof. The anode and cathode may be formed from the same type of CNTs or from different types of CNTs. For example, in one embodiment, the cathode can be a single-walled nanotube (SWNT), while the cathode is a multi-walled nanotube (MWNT). Furthermore, CNTs can be formed and processed by various methods. For example, CNTs can be generated by laser, arc, or other methods well known in the art. CNTs can also be treated by a variety of methods well known to those skilled in the art, including treatment with carbon dioxide, nitrous oxide, and the like; halogenation, including fluorination and chlorination; and treatment with organic conductive materials. May be. CNTs may also be combined with metal oxide materials currently used as active materials in Li-ion batteries, instead of carbon black. These processing processes are further described below. Additional information regarding CNTs useful in the present invention can be found in US Patent Application Publication No. 2004/234844 A1, the entire disclosure of which is incorporated by reference. Details regarding the use of lithium metal powder (LMP) in the anode and, optionally, the cathode are described below, the entire disclosure of which is incorporated by reference and incorporated herein by reference to Gao et al. Further information is disclosed in Patent Application Publication No. 2005/0131143.

The cathode of the present invention includes CNTs, but can have a variety of structures. The cathode may or may not be lithiated, and lithiation may be performed by any method known to those skilled in the art including the use of LMP. For example, in one embodiment, the cathode is formed from SWNT that has been electrochemically lithiated using a pure lithium counter electrode, a suitable electrolyte, and a separator. In one embodiment, the material is lithiated at low speed (<100 microA / cm ² ) for an extended period of time (˜20 hours per 0.5 mg of material). With this configuration, the cell voltage is ~ 3.0V before charging and ~ 3.2V for fully charged cells.

  In another embodiment, the cathode comprises CNTs that have been chemically modified by fluorination or other oxidation processes such as chlorination.

  In another embodiment, the cathode comprises CNTs treated with an organic conductive material, such as a conductive polymer such as poly (3-octylthiophene). Other conductive polymers that can be used for this purpose include substituted polythiophenes, substituted polypyrroles, substituted polyphenylene vinylenes, and substituted polyanilines. Ion doping of these materials, or self-doping by including a sulfonic acid group at the end of the alkyl chain, can make the conductive polymer p-type.

  In another embodiment, the cathode, instead of carbon black, combines lithiated CNTs with metal oxide materials currently used as active cathode materials in Li-ion batteries. This is a double advantage 1) that the nanotubes can provide higher electron conductivity to the resulting composite electrode to improve cathode performance, and 2) lithiated nanotubes can improve cathode capacity That can be provided. A high cell voltage can be preserved by the presence of lithium metal oxide in the cathode.

  In another embodiment, the cathode is CNTs lithiated with LMP and can be lithiated in any manner, including the methods described below for CNT anode materials. In some embodiments, the cathode and anode comprise the same CNT / LMP material.

With respect to the anode, the anode may be formed from CNTs capable of absorbing and desorbing lithium in an electrochemical system, wherein LMP is dispersed in the CNTs. The lithium metal is preferably provided in the anode as finely divided lithium powder. More often, lithium metal has an average particle size of less than about 60 microns, more frequently less than about 30 microns, although larger particle sizes may be used. The lithium metal may be provided as a so-called “stabilized lithium metal powder”, ie, the lithium metal has a low pyrophorosity powder by treating the lithium metal powder with CO ₂ and is well It is stable and easy to handle.

  The CNT anode can be reversibly lithiated and delithiated with an electrochemical potential for lithium metal greater than 0.0 V and 1.5 V or less. If the electrochemical potential is 0.0 V versus lithium or less, lithium metal will not re-enter the anode during charging. Alternatively, if the electrochemical potential exceeds 1.5 V versus lithium, the battery voltage will be inappropriately low. The amount of lithium metal present in the anode is the maximum amount sufficient to be intercalated or alloyed with or absorbed by the carbon nanotube material in the anode when the battery is recharged. The following is preferable.

  According to some embodiments of the present invention, the anode includes providing a CNT capable of absorbing and desorbing lithium in the electrochemical system, dispersing the LMP in the CNT, and the CNT and the interior thereof. The dispersed lithium metal can be produced by forming on the anode. LMP and CNT are preferably mixed with a non-aqueous liquid and a binder to form a slurry.

  Formation of anodes, or other types of electrodes, such as cathodes, according to embodiments of the present invention can be accomplished by combining LMP, CNT, optionally a binder polymer, and solvent to form a slurry. In some embodiments, the anode is formed by applying a slurry onto a current collector such as a copper foil or mesh and drying. Pressurization of the dried slurry on the current collector together forming the electrode completes anode formation. Pressurization of the electrode after drying densifies the electrode so that the active material can fit into the volume of the anode.

  In some embodiments of the present invention, it may be desirable to prelithiate the CNT material. For the purposes of the present invention, the terms “prelithiated” and / or “prelithiated”, when used in reference to CNTs, refer to lithiating the CNTs before contacting them with the electrolyte. Prelithiation of CNTs can reduce irreversible capacity loss in the battery caused by irreversible reaction with the electrolyte of lithium metal powder particles in the electrode in parallel with lithiation of CNTs.

  Prelithiation of CNTs according to some embodiments of the present invention preferably occurs by contacting the CNTs with LMP. For example, CNTs can be contacted with dry LMP or LMP suspended in a fluid or solution. CNT can be lithiated by the contact of LMP and CNT, thereby prelithiating the CNT.

  In some embodiments, the CNT and dry lithium metal powder are mixed such that at least a portion of the CNT contacts at least a portion of the lithium metal powder. Vigorous stirring or other agitation can be used to facilitate contact between the CNTs and the lithium metal powder. Contact between the lithium metal powder and the CNTs results in partial lithiation of the host material and prelithiated CNTs are formed.

  Prelithiation of CNTs can be performed at room temperature. However, in various embodiments of the present invention, pre-lithiation of CNTs is performed at a temperature above about 40 ° C. Prelithiation performed at a temperature above room temperature or above about 40 ° C. increases the interaction and / or dispersion between LMP and CNT and increases the amount of CNT that can be lithiated within a given time.

  Lithium metal powder becomes softer and / or more malleable when exposed to temperatures above room temperature. The softer lithium metal powder increases contact with the material mixed with the lithium metal powder when mixed with other materials. For example, the interaction and / or dispersion between the stirred metal metal powder and CNT mixture is less at room temperature compared to when the temperature of the mixture is raised above room temperature. By increasing the contact between the lithium metal powder and a reactive species such as CNT, the amount of lithiation of the reactive species is increased. Thus, increasing the temperature of the mixture of lithium metal powder and CNT increases the interaction and / or dispersion between the two materials, which also increases the lithiation of the host material.

  The temperature of the mixture is preferably maintained at or below the melting point of lithium. For example, the temperature of the mixture of lithium metal powder and CNT can be increased to about 180 ° C. or less to promote CNT lithiation. More preferably, the temperature of the lithium metal powder and CNT mixture can be increased between about 40 ° C. and about 150 ° C. to promote lithiation of the CNTs.

  In another embodiment, CNTs are introduced into a solution containing lithium metal powder. The solution can include, for example, mineral oil and / or other solvents or liquids that are preferably inert or do not react with the lithium metal powder in the solution. When mixing with the solution, it is preferable to stir the solution so as to promote contact between the CNT and the lithium metal powder. Contact between the CNT and the lithium metal powder promotes lithiation of the CNT to produce prelithiated CNT that can be used to form the anode.

  The lithium metal used in the various embodiments of the present invention may be provided as stabilized lithium powder (SLMP). The lithium powder can be processed for stabilization or otherwise conditioned during transport. For example, SLMP can be formed in the presence of carbon dioxide, as is known in the art. Dry lithium powder may be used in various embodiments of the present invention. Alternatively, SLMP can be formed in a suspension, such as a mineral oil solution or other solvent suspension. Formation of lithium powder in the solvent suspension can facilitate the formation of smaller lithium metal particles. In some embodiments of the present invention, SLMP can be formed in a solvent that can be used in various embodiments of the present invention. SLMP in the solvent can be transported in the solvent. Furthermore, a mixture of SLMP and solvent can be used in embodiments of the present invention, thereby eliminating the mixing step from the electrode manufacturing process because the solvent and SLMP are available as a single component. . This reduces manufacturing costs and may allow the use of smaller or finer lithium metal powder particles in embodiments of the present invention.

  The solvent used in embodiments of the present invention must also be non-reactive with lithium metal, binder polymer and CNT at the temperatures used in the anode or cathode manufacturing process. The solvent or co-solvent preferably has sufficient volatility to readily evaporate from the slurry and facilitate drying of the slurry applied to the current collector. For example, the solvent can include acyclic hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, symmetric ethers, asymmetric ethers, and cyclic ethers.

  Various binder polymer and solvent combinations were tested in embodiments of the present invention to determine compatible and stable binder polymer-solvent pairs. In addition, the anode formed from the binder polymer-solvent pair was tested to confirm compatibility. Table I lists preferred binder polymer-solvent pairs for use in making anodes and cathodes according to some embodiments of the present invention.

  It is understood that additional binder polymer-solvent pairs can also be used or combined to form the slurry and anode according to embodiments of the present invention.

  The separator and electrolyte can be selected from a number of well known in the art. In the present invention, the liquid / solid polymer electrolyte adds safety to this high energy system.

  Research efforts have identified polyphosphates and polyphosphonates (PEPs) as good candidates for polymer electrolyte preparation. In addition, both liquid and solid state electrolyte systems have been successful. These novel materials were relatively inexpensive to prepare in a one-step process and gave very good lithium ion transport properties of 0.5 compared to 0.3 for polyethylene oxide (PEO). Promising results were also obtained in the thermal stability test (stable to heat up to> 300 ° C.). To extend the operating temperature range from -20 to + 90 ° C, a polyphosphate liquid electrolyte can be blended with propylene carbonate (PC) to improve the low temperature performance of the polyphosphate material. These liquids are completely miscible with polar liquids such as PC.

  The synthesis of PEP is simple and a one-step process that minimizes production costs. After polymer synthesis, the lithium salt is dissolved in a fluid polymer at a concentration of 1M to prepare a liquid polymer electrolyte (LPE). The use of lithium bis-trifluoromethanesulfonimide (LiIm, 3M Co.) as the lithium salt in these electrolytes was very effective.

  The following examples are merely illustrative of the invention and do not limit the invention.

Example
Control A:
First, a control sample containing no CNT was synthesized. 9.65 g of mesophase carbon microbeads (MCMB) obtained from Osaka Gas Ltd were mixed with 0.35 g of PEO powder (Aldrich, 5 × 10 ⁶ MW). Next, 26.25 g of anhydrous p-xylene (Aldrich) was combined with 0.975 g of Lectro® Max stabilized lithium metal powder (SLMP). This was mixed for 5 minutes at ~ 300 rpm using an overhead mixer. The MCMB / PEO mixture was then continuously combined with SLMP in xylene. The resulting mixture was wrapped in tin foil to prevent solvent loss, heated to about 55 ° C. and stirred at about 300 rpm for 3 hours. The resulting product was a homogeneous black slurry, which was applied onto a piece of copper foil lightly polished with sandpaper, degreased with acetone, and dried in an oven prior to use. This was dried overnight on a hot plate in the glove box. When removed from the glove box, a small square of this material was cut out, pressurized and stored in a frozen bag with an argon-filled zipper and prepared for testing.

Control B:
The second control synthesized was a slurry formed from untreated CNTs. The procedure used was similar to Control A but scaled down to accommodate a smaller amount of CNT. An amount of as-received Hipco SWNT material was dried overnight under Ar prior to use. As with Control A, this material and all other sample preparations were performed in a glove box. The production method of Control A was followed except that PEO was omitted. As before, 0.02 g of SLMP was combined with 10 ml of xylene and mixed thoroughly. Next, Hipco SWNT (0.10 g) was added to the xylene mixture and stirred on a hot plate at about 55 ° C. for 3 hours. The resulting mixture was a homogeneous black thin pasty material that was spread on a large aluminum pan and dried overnight. Since the material did not adhere well after drying, the material was scraped from the pan and placed in a vial.

Sample material 1
This first sample material incorporated a laser-generated SWNT soot that was burned in N ₂ O at 600 ° C. for 20 minutes and then treated with CO ₂ at 750 ° C. for 1 hour. The procedure for combining CNT with SLMP was identical to Control B, except that 17 mg SWNT was mixed with 13 mg SLMP and enough xylene to form a fluid mixture. No binder was used. After mixing was complete, the material was dried at 55 ° C. on a hot plate in a glove box. Samples were collected and stored in vials until use.

Sample material 2
Second sample material, CO ₂ - incorporating processing Hipco nanotube (1 hour at 750 ° C. at 10L / min CO _2). The preparation method was similar to the method provided for sample material 1 except that 50 mg of Hipco nanotubes and 38.5 mg of SLMP were used. Sufficient xylene was added to obtain a fluid mixture.

Sample material 3
The third sample material incorporated arc-generated SWNT treated with ₂ L / min N ₂ O at 600 ° C. for 5 minutes. The preparation was similar to the method provided for sample material 1, but 22 mg SWNT and 10 mg SLMP were combined with 15 ml anhydrous xylene. The mixture was sonicated for 1 hour, stirred and sonicated again for 1 hour. The resulting mixture was a homogeneous ink-like suspension. This product was filtered in a glove box to produce nanotube paper.

Electrochemical results:
Half-cell test To confirm the relative lithiation quality of several prepared materials, various products were discharged against a lithium foil counter electrode in a standard laboratory cell. Generally speaking, the test was qualitative in that it did not measure the amount of test material. Cut small squares of each material and pressurize in a stainless steel pellet press using a hydraulic jack (the pellet press was kept in a bag with an argon-filled zipper when not in the glove box) for testing Prepared for. In FIG. 2, the discharge curves for several materials are compared.

As can be seen from FIG. 2, the open circuit voltage (OCV) of Control A is very low (120 mV vs. Li / Li ⁺ ), indicating that the material is highly lithiated. With the application of 100 μA discharge current, the cell voltage gradually increases, indicating the removal of lithium from the MCMB electrode.

FIG. 2 also shows the discharge curve for Control B. Control B is lithiated compared to Control A as shown by the relatively high OCV (˜1.0 V vs. Li / Li ⁺ ) and the higher polarization of the cell voltage when the discharge current is applied. Seems to be low. Nevertheless, at least 4 hours of discharge was required for the Control B electrode to reach 2.5V.

  Next, sample material 2 and sample material 3 were tested. As can be seen from FIG. 2, sample material 2 appears to have higher lithiation in the two samples, as shown by the relatively low OCV and slow polarization due to discharge.

After the half cell test, a series of experiments were conducted using different electrode material combinations in the full cell test. In the first test, we sought to determine whether the SLMP CNT electrode material could be used as an alternative to the electrochemically lithiated anode previously used in CNT / CNT cells. For this purpose, sample material A is used to form the anode, non-lithiated, CO ₂ treated, laser-generated SWNT bucky paper is used to form the cathode, and the cell is run several times as shown in FIG. Cycling.

  In this test, charging was performed at a much higher rate compared to discharging to bring lithium back into the anode (charging at 500 μA, discharging at 100 μA; 53 Wh / kg). As can be seen, a typical voltage plateau appears around 1.5V.

  Next, cycling of two electrodes formed from the same material is performed to drive all of the stabilized lithium metal powder from one electrode into the other, thereby developing a cell voltage, and Attempts were made to improve lithiation. This concept was first tested with Control A as shown in FIG. The first cycling was performed with a high charge rate and a low discharge rate to move lithium from one electrode to the other (charge at 500 μA, discharge at 100 μA). The total weight of material (both electrodes) in the cell was 38 mg. As can be seen from FIG. 4, the continuous charge improves the discharge capacity of the cell. With the third cycling, the cell shows 705 mV after 1 hour discharge at 100 microamps. These results indicate that this cell is a basic Li ion battery.

  As shown by the results shown in FIG. 5, further recycling of the Control A cell resulted in what appears to be a cell short and cell failure. Attempts to solve this problem by inserting additional separators were ineffective, i.e. the cell was shorted again.

  Next, a second test cell was prepared in which both anode and cathode were formed from sample material 2. The total weight of the electrodes in this cell was 8 mg. FIG. 6 shows the cycling results of this cell. The cycling criteria were the same as Control A (charge at 500 μA, discharge at 100 μA), but after the same number of initial cycling, the cell was at a higher voltage (1310 mV) compared to the Control A cell at the third discharge. showed that. The sample material 2 test cell appears to be much more efficient than the control A cell because there were 5 times more material in the MCMB control A cell than the CNT sample material 2 test cell.

  In addition, the short circuit and cell breakage problems appear to be much less severe in the sample material 2 test cell, where the cell was cycled more than 12 times (charged at 200 μA) as shown in FIG. And discharge). FIG. 8 shows further evidence that the sample material 2 test cell has a higher efficiency than the control A cell, where the capacity of each cell for a one hour discharge in the seventh cycle is compared. As can be seen from FIG. 8, none of the cells discharge for a long time, but the capacity of the CNT cell is much larger than that of the MCMB cell.

  While certain embodiments of the invention have been described, the invention as defined in the claims may be subject to numerous obvious variations without departing from the spirit or scope of the claimed invention. As such, it should be understood that it should not be limited to the specific details set forth in the foregoing description.

It is a figure which shows the embodiment of this invention. It is a graph which shows the half cell discharge test of the embodiment of the present invention. It is a graph which shows the cycle test of the embodiment of the present invention. It is a graph which shows the cycle test of the embodiment of the present invention. 5 is a graph showing further cycling of the embodiment shown in FIG. It is a graph which shows the cycle test of the embodiment of the present invention. 7 is a graph showing further cycle testing of the embodiment shown in FIG. 4 is a graph comparing embodiments of the present invention with prior art materials.

Claims (8)

A battery comprising: an anode in electrical communication with a cathode; a separator separating the anode and the cathode; and means for electrical communication between the anode and the cathode;
A battery in which the anode and the cathode are carbon nanotubes, and the anode is a carbon nanotube lithiated with lithium metal powder.   The battery of claim 1, wherein the carbon nanotubes are selected from the group consisting of multi-walled nanotubes, single-walled nanotubes, nanohorns, nanobells, peapods, buckyballs, and combinations thereof.   The battery according to claim 2, wherein the carbon nanotube includes a single-walled nanotube.   The battery according to claim 1, wherein the separator includes a lithium salt electrolyte.   The battery according to claim 4, wherein the electrolyte is a phosphate or polyphosphate electrolyte.   The battery according to claim 1, wherein the carbon nanotube has a reversible capacity exceeding 600 mAh / g. The battery according to claim 1, wherein the carbon nanotube has an alkali saturation of MC ₈ (wherein M is selected from the group consisting of K, Rb, and Cs).   The battery of claim 1, wherein the cathode comprises single-walled nanotubes and the anode comprises multi-walled nanotubes.

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